Yes, the Delkin Devices POWER CFexpress Type B 128GB is compatible with the Nikon Z6 III.
Delkin Devices POWER CFexpress Type B 128GB has a manufacturer-rated 805 MB/s sustained write speed (no official VPG certification for this SKU), clearing Nikon Z6 III's 250 MB/s requirement for 4K60 (Nikon's own manual states this as a raw sustained-write floor, not a class rating). Type B slot confirmed on Z6 III.
“Nikon Z6 III product page: Dual Card Slots — SD UHS-II + CFexpress (Type B)/XQD; CFexpress Type B cards supported in the dedicated CFexpress/XQD slot.”
Last verified:
Compatibility inferred from spec rule (citations above are manufacturer-verified)